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Old 07-11-2009, 08:54 PM
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Default TIG welding stainless - Help?

At work, I often get called upon to weld stainless. I can do it, but I would like to know if their are any tips and/or techniques to make things come out more, ummm, presentable?

I can weld stainless ok, 16ga and over. It is the 18 & 20ga stuff that gives me fits. I can't keep a consistent puddle without melting away the edges and sometimes leaving a hole. If there is a gap, things often go terribly wrong and the filler rod gets used more as filler than anything else.

Yes, nice, clean, even, as small as possible gaps help somewhat, I even have problems there. Besides that, neat, clean, even gaps often do not present themselves in maintenance welding. My bosses likely wouldn't much appreciate having new parts fabricated every time. As ugly as some of my welds are, they stick just fine when I'm done, so replacing instead of repairing would not be cost-effective.

Ok, I think I have presented just about every hurdle a welder needs to overcome as far as fit up and condition of the pieces - any ideas? I usually spend way too much time finishing my welds and am still left unsatisfied with the results.........even though I'm the only one complaining about it.

Any help?

Tim D.
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Old 07-11-2009, 09:59 PM
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Shobra Shobra is offline
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Default Copper

When ever possible I use copper backing with stainless. This is more to help hold some shielding gas in-place on the back side of the weld. Where I can't get a copper backing plate I have used the Foil tape that you use on ducting. Doing this I've come to get almost as nice on the backside as the front.

I've also heard that on non-structural parts you can use dry ice. A little work and you can make it fit a piece of stainless trim (like on the side of a 47 ford). The carbon dioxide that it releases help act a shielding gas and the cooling from the ice helps to make welding the thin stuff easier. Not to be used on a Structural part because of the temperature differences.

As far as blowing holes... maybe someone else can chime in.
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Old 07-11-2009, 10:26 PM
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Dry ice? We have dry ice on hand (for blasting)! I think it has something to do with the inert gas effect too (carbon dioxide, dont ya know), as well as heat sinking. Access to the backside is very, very limited on most of these parts.

I tend to keep the current at around 1 amp per thou, though I actually have a bit better luck when I use a bit more juice............not always, but sometimes anyway

Tim D.
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Old 07-11-2009, 10:26 PM
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Default Tig welding

Hi Tim
you realy don't want any gaps at all on 18g or 20g, the better the fit the better the weld.

Coppers fine behind the weld, but if you run argon on the back of the weld,you will get a better weld.

Masking tape stuck on the back of where you are welding works really good. (stops the air from contaminating the back side.)

The masking tape burns and is a bastard to clean off, but the welds come up a lot nicer

If you have gaps,thicker filler wire helps a lot

All the best
phil
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Old 07-11-2009, 10:44 PM
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Default Tig dvd

Tim
Ron Covells Tig Welding Dvd was was really good to see for me even after welding SS for 30 plus years

Phil
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Old 07-11-2009, 10:54 PM
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I wish I could show pics of the parts I'm talking about.....but that is strictly verbotten.

I'll have to try the tape trick! The gaps usually come from the incident that brought about the need to weld it back together My metalshaping skills sometimes get called into play to "unshape" things. Not having gaps would be great, but often isn't possible. The joys of "maintenance welding"! I'll have to check out Ron's DVD too.

I have thought about rigging something up to backgas the weld.......but it would have to be something easy to do and undo since it isn't my welding rig.

This is mostly a matter of pride and self-improvement for me, especially in light of some of the "boogers" I've seen applied in the workplace. While I tend to weld it as well as I can and then grind off the nasties, I would prefer to not have to spend a lot of time on nasty stuff that doesn't need to be there anyway, ya know?

Thanks for the tips so far!

Tim D.
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Old 07-12-2009, 12:20 PM
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This is more of just thinking outloud than anything so if there is something wrong please correct me.


I haven't tried masking but like I said before the foil tape works, it does leave the glue residue behind. I will make a (small) tent shape over the weld (with the foil tape). I've also used that fiberglass material that you can find around your oven door (it's inside the seal) and then held it in place with the foil tape, but I didn't like that method. Warning Don't take apart the oven seal in your house to try this or, you may not be allowed back in the house.

If it's a small enclosed space you could seal the ends with the foil tape and drop a small piece of dry ice in the space, this could create a purged space of co2 to shield the backside of the weld. NOT to be used in fully enclosed spaces (like a tank) without a vent so as no to blow yourself up with the pressure created. If I remember the C02 is heavier that the surrounding air use that to your advantage.
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Last edited by Shobra; 07-12-2009 at 12:26 PM.
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Old 07-12-2009, 03:28 PM
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If you can back purge with argon if not copper strip if not oh well. Try using less current than you think 20 swg ss you probably only need 20-30 amps make sure that your tungston is ground to a very fine point and if at all possible dress on a diamond wheel to reduce as many of the grinding marks as possible , use a foot pedal or thumb wheel to control the current and take your time , remembering that you want to use a filler rod dia that matches the thinkness of the material that you are welding .Trying to weld thin metal ie 20 or 18 swg with a 1/16th rod is a nightmare think about it the base metal has melted and dropped throught long before the filler has enough heat in it to melt. I weld quite a bit of 18swg s/s both brushed and mirror polished in my day job i use 30 thou 316 mig wire and generally have no problems alot of the welds will be on corners of folded sheet where only the inside edge's of the sheet touch copper behind them and take my time . Hope this helps
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Old 07-12-2009, 07:37 PM
Norm Swenson Norm Swenson is offline
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Seems like the consense is to go in as cool as you can, then take your time to lay your bead. I guess I'm going against the grain again 'cause the way I do it is a little different. I like to use .040 tungstun. .030 filler rod, approx. 1amp/.001 thickness. I set my machine so I go full pedal right from the get go. Go in hot , then as soon as I get a partial puddle, dip my rod in to add filler and use it as a heat sink also. Then the most important thing is to move FAST. Dip and move as fast as you can. While I've never checked my speed I bet its about 12" / min. or so. The idea is to get the metal as hot as you can as fast as you can, then add filler to cool the weld before it can blow out. I've tried copper before but if I dawtle (go slow) I still blow out. Speed seems to be the only thing that works consistently for me. While back gassing may help the looks of the bead , front and back, probably purity also, I can't see how it will help from blow thru. But I got to admit, I have not tried back gassing yet.
Hope this helps some. Also I'm NOT a pro welder. Just a hack playing in the garage.



Norm
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Old 07-13-2009, 02:38 PM
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I'm going to contradict myself here abit I sort of agree with you norm , in that if i was doing something like the described job myself i would got hot and fast like you have said but i'm no pro welder either but i probably put down 2 or 3 miles of tig weld a year yes thats miles not yards , as such i have to use big amps and run fast , time is money and all that. But form someone who doesn't do a lot of tig welding they are probably far better of filling a gap by building up tacks so it looks like a row of dime's as you say the sort of way alot of people mig weld panels "hot stitch " i think you call it , i'd call it a big bunch of tacks on top of each other.
Hope this might help also Tim

Cheers Chris Cant
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